If you are going to buy and leave it for a few years without trading it, I would recommend IOTA.
IOTA was developed by the IOTA Foundation is a gemeinnützige Stiftung (i.e. non-profit Foundation) located in Germany. with the aims to simply provide an IoT solution that leverages blockchains security and incentive mechanisms without the drawbacks of fees and transaction scaling.
To resolves the problems of transaction costs, scalability, and offline transaction, IOTA was hence developed. IOTA is a completely open source and a non-profit organization focused on building an IoT solution inspired by, but not based on blockchain technology.
Some say IOTA is new and there is a huge potential in its project. That is not entirely true. IOTA development began with hundreds of supporters back in 2015 and it has been covered in TechCrunch, VentureBeat, Forbes, Cointelegraph, CIO, etc. repeatedly. It is not a new project and they have been there for a while now.
Although it is not a new to some of us, in my opinion, IOTA is still far away from mass-adoption.